Have you tried rubbing the hairball medicine into her fur? I have a cat who can fling gobs of the stuff great distances, but when I rub it in enough that it's no longer a glob, he manages to get most of it into his insides. Of course, I have to hang onto him for dear life when I'm doing this...

Hairball medicine is very hard to clean completely off of anything. You've got my sympathies.

And yay for finding the bottom of the bottle of antibiotics!